Wet plasma conditions

On line additions of aqueous standard solutions for the calibration of LA-ICP-MS including a comparison of wet and dry plasma conditions are discussed by O Connor et al.ls For solution calibration of standard solutions the authors used a 100 (xl PFA nebulizer together with a cyclonic spray chamber or a MCN-6000 sample introduction system with desolvator, to study the wet and dry plasma, respectively. A polypropylene Y piece was applied to mix the laser ablated material and the nebulized standard solutions. The authors found that the on line addition of water is the preferred mode of operation for quantification by LA-ICP-MS, i.e., wet plasma is more stable (improved standard deviation of sensitivity ratios). 

Figure 30.9. LPCAT treatment under stronger plasma conditions for a longer time yields the more wettable surface. However, the sessile droplet contact angle of a paint on Parylene C surface (resident time 0) is low and minimal change occurred with LTCAT treatment. Thus, the adhesion problem is not due to the wetting difficulty.

MeHg using isotopically enriched Me Hg and Bus Sn wet and dry plasma conditions used to facilitate mass bias correction and signal optimization CRM 710 analyzed to validate method... 

O Connor, C., Sharp, B.L., Evans, P. (2006) On-line additions of aqueous standards for cahbration of laser ablation inductively coupled plasma mass spectrometry theory and comparison of wet and dry plasma conditions./oMrnaZ of Analytical Atomic Spectrometry,21, 556-565. 

A drawback of all these solution-based techniques are the different excitation processes between wet and dry plasma conditions occurring in the ICP, resulting in different signal responses... 

The classical wet-chemical quaUtative identification of chromium is accompHshed by the intense red-violet color that develops when aqueous Cr(VI) reacts with (5)-diphenylcarba2ide under acidic conditions (95). This test is sensitive to 0.003 ppm Cr, and the reagent is also useful for quantitative analysis of trace quantities of Cr (96). Instmmental quaUtative identification is possible using inductively coupled argon plasma—atomic emission spectroscopy... 

The resist has been used as a mask in wet etching and in lift-off processes, and more recently in etching chromium films in a chlorine-oxygen-helium plasma. In the latter, the etch rates have ranged from 4 to 5.5nm/min at lOOW power in a barrel type reactor. Chromium etches at about 6.5nm/min under these conditions. The etch rate of the resist appears to be independent of the degree to which it has been cured before exposure, so the sensitive form described here is just as effective a mask as the highly cross-linked resists described earlier, at least in the chromium etching process. 

Plasma processing is used extensively to deposit and, in particular, etch thin films. Plasma-enhanced chemical vapor deposition allows films to be formed under nonequilibrium conditions and relatively low process temperatures. Furthermore, the films have special material properties that cannot be realized by conventional thermally driven chemical vapor deposition processes [8,9]. Plasma etching (dry processing) has almost totally replaced wet etching since it provides control of the shape of the microscopic etch profile [27]. 

The analytical procedure employed is shown in Figure 122.3. Approximately 0.5 g of a powdered sample was mixed with V2O5 and placed in a quartz boat. The boat was then placed in a quartz tube and the sample was heated to 1100°C under a wet oxygen flow (pyrohydrolysis). Iodine evaporated from the sample was collected in a receiver TMAH solution. The iodine in the receiver solution was determined by inductively coupled plasma mass spectrometry (ICP-MS Hewlett Packard 4500 Model). The operating conditions of ICP-MS were as described in the earlier report (Muramatsu and Wedepohl, 1998). Its detection limit is 0.3 ng ml (ppb). The analytical procedure was checked by using standard materials, e.g., NIST SRM 1537a (tomato leaves), 1549 (milk powder), 1572 (citrus leaves) and so on (Schnetger and Muramastu, 1996). 

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